Why I'm Making My Own Brakes

lambertius

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341
I’m fascinated by all of this and albeit I don’t understand most of it I almost just want to buy some (even though I don’t own a 4200), it’s simply because it can prove Masser parts can be supplied in Australia in AUD!

I’ll grant you none of the above makes sense but then I gave that up on page 2 of this topic....

Short version is that I'm spending a lot of time looking at catalogues to make sure off the shelf parts fit. Everything else is really just for a bit of fun to take the opportunity to learn a bit more about the technicalities of what is going on. Anyone can do this is a set of vernier calipers and a catalogue which is why there are a lot of options out there, though they're not typically engineered but rather built. An example would be the way I designed the mounting hats, DBA uses 6061-T6 to make their hats for road and race use, I know its cost effective so I'll use it to. I could've just ended there but I was interested in other design considerations such as load failure and the endurance limit, so I'm just posting it up as I play with things.

I'd have finished it a while ago had I just one thing going on, but you know, life.
 

lambertius

Banned
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341
So I have spent about 20 hours reading catalogues for the rear rotors now - and I think it should be possible to squeeze a 2 piece rotor on the back and keep the factory hand brake - but it really comes down to what the factory diameter is for the OEM rotor. If anyone has it, or can measure it then I will know for sure if I can fit it!
 

lambertius

Banned
Messages
341
I have found the data on the offsets, at last. Tarox has them.

Ferrari 456 Front (Offset 62 mm)
Ferrari 456 Rear (Offset 81.5 mm)
Ferrari 550 (Front Offset 61 mm, Rear Offset 80 mm)
Maserati 3200 (Front Offset 61 mm, Rear Offset 80 mm)
Maserati 4200 (Front Offset 61 mm, Rear Offset 80.5 mm)

The diameters and the PCDs are all the same. Maserati says that the rear rotors for 3200 and 4200 are the same, so Tarox's measurement may not be reliable, however.

Just remembered this post, thanks! I measured 312mm for the rear, so anyone who can help by confirming one way or another would be met with much friendship.

71473

Also, if it is relevant to anyone in the future, I believe this is the OEM specs as per brembo for the front rotors

https://www.bremboparts.com/europe/en/catalogue/disc/09-6802-20

71474
 

lambertius

Banned
Messages
341
More updates!

With the front rotor I got my quote back for my ultralight hat - unfortunately infinity dollars is too much, so I dropped back to something more sensible. The below design is pretty much standard fare. The scallops around the mounting points isn't there for weight reduction, but to reduce heat conduction through to the aluminium.

I will be making them out of 6061-T6, this is the same grade that is used by DBA and a bunch of others. It knocks the weight down to 1/3rd compared to steel of the same dimensions and is nearly as strong. The V8 Supercars use this as the material for the hats on their rotors, and I imagine its the same for all touring cars.

I included a screen shot of some off the shelf rotors with hats by DBA for comparison. The chamfered edge towards the mounting holes is significantly stronger than going into a flat edge, and it had a negligible effect on costs, so I'll keep it. One little thing I did that was my own idea was chamfering the centre bore. Whenever a rotor sticks to a hub, its always due to the centre bore. The thing is though, the centre bore is never under any load, so it doesn't need to be a significant structural component. By tapering the edge down it will be much easier to get the rotors on and off in the future.

71493

On the inside edge of the hat there is a 3mm fillet (rounded edge) which will prevent stress from focusing in the flat top.
71494

There is a 3mm clearance between the hub and the inside wall. This tiny clearance was one of the most troublesome items. Finding a rotor with a large annulus and a small rotor PCD was very difficult.

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71495
Below is the rotor the hat is designed for. These directional vaned rotors are used locally on a range of HSVs, and I believe they are used on Corvettes in the states.
71490

Due to the unusual requirements of annulus and rotor PCD, I was only able to find two rotors that fitted over our hubs without any compromises. One was this, and the other is a rotor at Wilwood. The high vane count of this rotor allows the rotor to be a bit heavier, so a better thermal mass, than the Wilwood and being available locally made it a much cheaper choice for me as shipping is pretty hefty on slabs of steel.

I contacted Wilwood, Brembo, Alcon, AP, DBA and a couple of smaller players and went through hundreds of pages of catalogues. There are other rotors which could fit without modifying the position of the caliper, but they would introduce other compromises such as needing to run a thinner rotor. If I got the pad placement absolutely perfect I could run a couple of other rotors as well, as the minimum annulus is 57mm, but to go down to exactly 57mm on the rotor I'd need to get the centre point perfect otherwise I risk running the pad over the edge, and since I found a couple of fits that worked it wasn't necessary to be that pedantic.

The rear rotors remain somewhat more problematic. The culprit is the highlighted part of the hub, it dictates that the hat must have an internal diameter of 180mm to clear the part, if you include wall thickness then you've got 190mm used up. Working in radii to make the problem a bit clearer:

Outer radius is 160mm
Take away 55mm for the annulus which leaves us with 105mm spare.
Take away 95mm for the hat and you're left with 10mm to mount the hat.

The rotor PCD must occur between 190mm-200mm. Most rotors (regardless of size) have a mounting PCD ~205mm (this is what made it hard to find the front rotors).

I've only found one rotor that meets the bizarre requirements of a huge annulus and small rotor PCD, but there is a compromise in that it isn't 28mm thick but 25mm. The only other candidate I could find was 32mm thick and just won't fit outright, I would need to machine the rotor face. I mean that is fine to do as that is what people do anyway as rotors wear out but it seems a bit of a waste on a brand new rotor. Instead it is easier to fit a thinner rotor and to shim the pads out to prevent the pistons running out so that is what I'm looking at doing currently. I still need to confirm though if the annulus is 55mm or 50mm as that makes a substantial difference to the rotors I can choose from.

71497

I'd really like to know what rotor Zep used on his front kit. It looks like an AP Racing, but I couldn't find anything in their catalogue that would've worked up front on the standard sized pads. If you don't mind letting me know who you went with, they may have a better candidate for a rear rotor since the seem to carry unusual sizes?

A friend of mine suggested just making my own rotor for the rear out of billet. I mean, it would work technically but lol, no.

I also have a sneaking suspicion that the front calipers will fit onto the rear. A very helpful forum user is going to try and measure that up for me, but if that were the case it would open up an interesting possibility. The front and rear calipers appear to be almost the same with effectively identical piston area and pad area. I can really only put down the difference in caliper size to cosmetics because I can't see a practical reason why they're different. It also doesn't make sense that they have quick release pads on the rear but pins on the front. Anyway, getting a set of front calipers on the rear would also address the issue as I've already got a rotor that fits.

For a bit of fun, this was the final version of the ultra light hat:

71498

71499

See what happens!
 

lambertius

Banned
Messages
341
Turns out I can get my rotor hats anodised any colour I want. What colour would you all pick?

71537

So I have some solid costs now (in AUD):

$288 per front rotor
$334 per rear rotor
$361 per hat (including shipping and finishing)

All up it would be $1578, or about 850GBP. Compared to getting new units from eurospares, it is a little bit more in direct costs as the parts would be $1140, but there would also be around $300 in shipping. So I'll be charitable can say that my bits are $1600 v $1400. If you tried to get the parts through a dealer though.... oof.... Compared to FD, all four would be ~$1600 before shipping for the OEM replacements. I've seen front only kits that are still cross-drilled, or require skinnier pads at between $1200-$1600 for just fronts, before shipping.

Anyway, its looking like its worth my effort, and these rotors will probably last longer than the rest of the car does...

Design wise, everything up front is finished and I just need to step up and press buy. The rears I need to measure a few more things. It would appear that the rear calipers will hold a 30mm wide rotor and if that is the case then I will be able to directly fit a couple of rotors. I also searched through a bunch of pads that would fit, and found a couple a bit thinner which would accommodate the extra 2mm if needed. If I can squeeze a 32mm rotor in then things get a lot better, but I doubt it. If the 30mm thick rotor will fit, DBA52650.1 would be a prime choice to accommodate the OEM handbrake.

I am debating on ordering the front rotors and hats now and resolving the rears later as I can't measure the critical dimensions on the rear till I get home in a few weeks. The other part of me wants to do it all in one go...
 

Twinspark

Member
Messages
460
That's actually a pretty good price and similar to what FD offers for what I assume would be better performance / more longevity. I would have considered it but I got my car with the FD 6 piston BBK so I think its got bigger rotors than standard.

How's the control arm project going on?
 

lambertius

Banned
Messages
341
Those are the prices as cost, FD is a business and has to run overheads whereas I'm just some dude harassing companies to supply individual parts. On the other hand, it does show that the OEM parts are over priced.

I would say what I'm doing would likely have better longevity as they're not cross drilled which is better for both the life of the rotor and the pad. Performance wise, unless you're hammering a track it honestly isn't likely to be truly noticeable, but I will do some braking tests before and after I install everything. Below are some results on my MX-5.

71546

The control arms are coming along fine, but I haven't done much on them since looking for bushings as it is just effort and I wanted to play around with a few other things. I haven't had my car at home to measure up for nearly two months so that slowed down a smidge. I focused on other projects like the brake testing, I finally finished my MX-5 SP, restored my headlights, rebuilt a window regulator and installed new brakes on my BMW and a few other things I've been hanging on to.

71548

71549

I'll get it done, but it is time consuming and every now and again the mood will come and go. I feel like actually finishing something and I was closer to finishing the brakes so I thought I'd crack onto that again.
 

lambertius

Banned
Messages
341
Things are going well!

A wonderful chap has been following this for a while and got hold of me, he is based over in Queensland, and he pulled apart his brakes and confirmed a bunch of measurements for me as well as getting a few things I had missed but didn't realise until I needed to know! He sent me a bunch of photos over the last couple of days, and even took his brakes off the car! Legend!

Right now I'm finalising some choices for bolts lengths, and double checking things, but all the big decisions have been made, so I'll run you through it.

Front Rotor

I found two rotors that would fit all the limitations:

Willwood 150-15256 - This rotor meets all the requirements, is a directional vane rotor and hat an 8 hole mounting pattern.

DBA5048.1L/R - Available globally, but most importantly locally for me. It has a 12 hole mounting pattern, which I like as it would distribute the load more. Availability was the main factor here.

Here is an transparent screen shot of the rotor model:
71593

The OEM annulus is 61mm, and since I measured the area swept by the pad as 57mm there is plenty of area for the pad:

71594

Total height of the rotor and hat is the OEM spec is 60.7mm to ensure it fits with the factory calipers:
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Thickness of the hats is 7.4mm, which I measured for both front and rear:
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Rear Rotor

I needed to get creative with the rear rotor. The below solution was the best I was able to come up with, and it was only possible with the help from Chris. He verified that the maximum clearance in the rear rotor was 30.5mm, which gave me a half decent choice for the rotor. The difficulty in fitting a rear rotor was ridiculous. I spent maybe four days in total just going through catalogues!

This is the DBA52650.1, it is a 316x30mm rotor. As it is right now, the rotor won't fit. The maximum clearance for the rear caliper is 313mm, and the mounting lugs would
protrude into the handbrake. However, because I can fit the 30mm width, I don't need to play around with the caliper, and it is only slightly oversized.

71597

The solution is to turn down the outer edge by 6mm, and to turn out the original mounting lugs. I'll put 12 mounting points instead of 8 to better distribute the load, and I won't bother remaking the lugs as and just leave it solid.

71598


Shaving it down will just hit the pillars on the outside. On the inside there is enough of the original mounting lugs to use, but I need take off a bit more on the inner edge to allow clearances for tools to tighten the fasteners. Oddly enough the disk will be slightly stiffer this way as the mounting points are closer to the pillars.
71599

71600

Chris also confirmed the area swept on the pad as 50mm. This is a critical dimension, if it was 55mm I would've needed to get creative with the mounting holes.

The blue line is a 50mm swept area:
71601

The blue line is a 55mm swept area:
71602
 

lambertius

Banned
Messages
341
This is the whole assembly below:
71603

In order to mount the hat, the fasteners will need to come in from behind and tap directly into the hat:

71604

This transparent render shows how it will mount into the hat:
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Total height of the assembly is the OEM 80.5mm
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Here is a transparent render so you can see the pillar design, DBA refer to it as the 'Kangaroo Paw'.

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It is important to go over things and then check again! I found a discrepancy between some of the dimensions I was provided by DBA, and their drawings. I called up to confirm, and I had been given the wrong dimensions! Very lucky, that would've been an expensive mistake otherwise!

71608

I also did some thermal expansion calcs on the rear rotor to ensure running oversized won't clash with the caliper. Being conservative, the 30mm rotor could expand to 30.2mm if it were to reach 600 degrees, which it never should.

Right now all the design work is done, just making a few little checks and changes. The last thing I need to do before getting my parts is select some appropriate fasteners as they will dictate the thickness and thread length of the mounting points.

I've also spoken with Hawk and they have a whole range of pads that will fit both the front and the rear of the car, and since they provide nice little temp charts, and just recently sent me their most up to date one, I'll select a set from them! Only AP Racing provides as much data, but none of their hardware was going to fit.

71609
 

lambertius

Banned
Messages
341
So a big post!

Today I finally resolved the issues with the rear rotor and have finalised the parts and design. I thought I'd take you all through my adventures! I needed quite a bit of help to finalise the last few things, and I harassed DBA until they put me in touch with one of their engineers to answer the remaining questions I had. I had to do this because the packaging at the rear is just too tight.

So the design problem comes from the 338/M138 being old. Before the late 00s, large rims weren't common and so limited the diameter of brake rotors. Our cars hard large rims for the time, but due to the development cycle our cars are a 90s car in terms of technology. When you have a heavy, powerful car and not much space for brakes, how do you make them bigger? In the 90s the solution was to run very tall pads. This means that our rotors have a small (large for the time) outer diameter and a large annulus. This means that the rotor only has limited internal space for mounting hardware. When a rotor is a single piece this is much less of an issue, but for me, and especially on the rear rotor, this turned out to be very difficult! As I've gone through this I've gotten a couple of PMs about people wanting to do this themselves, so this is a loose how-to get all the parts yourself.

Front Rotor

71971

For the front rotor, the larger annulus meant I could only find two off the shelf rotors that would fit:

Willwood 150-15256
DBA5408.1R\L

As I've said previously, I went with DBA because of the ease of availability. DBA is a global company, with distributors around the world, so you would be able to get these rotors wherever you are.


USA
UK

Contacting them is quite productive and they will put you in contact with distributors. Locally the rotor costs $288AU and it is a directional vaned rotor with a slotted annulus. A thicker 34mm version of this rotor is used on the V8 Supercars.

In order to get correct fitment in CAD, I measured up the original rotor - and with the help of google and other forum members - I created a profile for the height of the original components and drew the hat in those boundaries.

71973

In order not to clash with the hub, I also drew a reference sketch for the hub. I then drew several guide circles in order to ensure clearance. Fitment is quite snug with a clearance of 4mm (2mm per side) as I needed to make room for the bolt holes.

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71975

The inside diameter is 163.16mm, the rotor PCD (the diameter that the bolts run through for attaching the rotor to the hat) is 182mm. This means I have 9.42mm to fit the walls of the hat, and a 1/4" (6.4mm) bolt hole.

The solution was to slant chamfer the outer edge to provide as much rigidity as possible. I also needed to create a little cutout to accommodate the head of the bolt. There is <1mm clearance between the bolt head and the edge of the hat.

71976

The bolts DBA use on their setups are NAS bolts. NAS is an aerospace product with yield strengths close to double 306 stainless bolt. The issue I had was that I can't use the hex head bolt due to fitment reasons, and with such a tight tolerance I had have precise parts. As I'm designing my own hats I also needed to make sure that I had the depth set correctly as the below are shoulder bolts. If I had the hole depth set incorrectly, then the nut would hit the grip (shoulder) before hitting the rotor and the assembly would be loose. I set about looking for drawings of the bolts so that I could set the correct thickness of the parts, which turned out to be very hard.

71977

You can see in the below cross-section that if I didn't have the thickness correct, the nut would hit the grip. If I had the bolt too shallow, there could be load from the rotor on the threads which is also bad.

71978

As I needed to select my own bolts, I ended up asking about the choice of thread (UNF instead of UNC), and it wasn't an arbitrary choice. The engineer said:

"They are UNF as the fine pitch is preferred due to its proof load and small lead angle. The crimp nut thread engagement on UNF enables a low profile body.

NAS bolts have a ground shank too.



So bolts. You want to drive the hat/rotor union on a bolt shank not the thread.
"

So I needed to look for a specific bolt. I eventually came across these guys https://www.aaestore.com.au/ who supply aerospace fasteners. They told me about http://everyspec.com/ where I could find drawings and technical requirements for every fastener you can imagine. After going through their catalogue I eventually came across a socket head cap screw that is MIL (military) spec that would be suitable. The series of bolts I settled on was MS20004. These bolts have a fixed 0.5" thread, and the rest of the bolt is shank. I then pulled up the current standard, which is from March 1989, and used it to accurately model the bolts so I could ensure the fitment. The document is a bunch of drawings and call outs. It takes a fair bit of back and forth to check the dimensions.

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71980

I fed some relevant information into a design table in my CAD program so I could 'test' fit several lengths.
71981

For the front rotor I will need 24 x MS20004-6 at $5ea. I'll use the crimp nuts that are supplied with the rotor as these are the correct thread.
 

lambertius

Banned
Messages
341
With the results correctly dimensioned I was able to get a quote on the part (and get it anodised red). $523USD for a pair out of 6061-T6.

71982
I'm really quite pleased with the front rotor - there are no compromises. This rotor isn't thinner, I don't need to go fiddling with brake pads or dog bones, and I get away from the issues and costs of other kits by quite a substantial margin. The cheapest front only kit I could find was ~$1600AUD before shipping. To equip the front setup as detailed above I'm looking at $1448AUD including shipping.

Rear Rotor

The rear rotor was just the biggest pain, and it was made harder as it wasn't until I found a supplier for the MIL spec bolts that I had a way forward. Before that I was using McMaster Carr as all their bolts come with drawings and CAD files, but they didn't have anything quite the right dimensions. More on that in a bit.

71983

I found several rotors that were good candidates, but everything was a compromise. None of the rotors were the correct dimension in every direction.

The closest I could find was by Alcon DIV2235X562C48. This would probably be a decent matched rotor for Zep's kit as it is a racing fish hook design with direction vanes. However, I decided not to go with it as I didn't like the position of the mounting lugs. Ultimately I went for a rotor that was oversized in every direction so that I knew I would have enough material to remove and get a correct fit. I settled with the DBA52650.1. This is a bi-directional pillar rotor used on a number of Subarus. It is a 316x30mm rotor, has a massive annulus and lots of material in the centre for mounting. Due to the changes I would need to make, I spoke with the engineer who designed this specific rotor to find out the minimum thicknesses, and consequences of any changes. Because this rotor is so thick and heavy it turns out that the minimum thickness for the rotor would be ~25mm, so taking this rotor down from 30mm to 28mm for my application would be acceptable. These rotors are $667AUD a pair, and machining will be another $100 per rotor.

Before:
71984
After
71985

The real trouble came with clearing the handbrake. For whatever reason, even the handbrake is oversized. I tried about a dozen variations of the rear hat until I found the MIL spec bolts.

I thought about tapping into the hat directly, but the engineer advised against it:
71986

I thought about mounting from the other side and using little windows to fit the nuts. The problem with this was that it blocked off the ventilation. I couldn't do this from the top as the little holes would conflict with the handbrake surface. The idea itself isn't that cray, Wilwood use it on some products.
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71988

The handbrake interface inside the hat:
71989

I tried to make a conventional flange fit and used some clever low profile fasteners, but there was no way it wouldn't clash with the calliper.

71990
71991
 

lambertius

Banned
Messages
341
The gap between the calliper and hat is only 8mm!

71992

I tried the inverted mount again, but this time with ventilation cut into it. This would've worked but the machining costs would've piled up....
71993

When I finally found the MIL spec bolts, I was able to come up with a much more appropriate design. I ran the long bolts all the way to the top of the hat, taking off only enough material to allow the nuts to fit. This meant that my costs were reduced slightly as I could use the supplied nuts with the rotor. It also meant that I could keep the shank as the only interface with the hat and not the threads, there is no risk of the threads pulling out of the hat, and because I had accurate drawings of the bolts I could ensure there are no clashes or interference.

71995
71996
71997

Everything is unbelievably snug and it wouldn't have been practical do this conventionally, too many expensive mistakes to make! Being able to test fit parts in CAD has made this viable for me to do. I don't have a current quote for the rear hat, but the last one I had was $600USD. I'm expecting this one to be similar, if not slightly less as it is simpler. So I would have 16 x $5 for the bolts, $863 for the hats and $887 for the rotors. So $1810 for the rears.

All in, front and rear setup would be $1448 + $1810 = $3258AUD. Right now that is about $2300USD and 1800GBP for a full two-piece rotor setup. About double what the OEM rotors would cost, but I get rid of the cross-drilling which is what kicked off this whole saga in the first place. Depending on where you are in the world you might even be able to pull it off cheaper if your local DBA supplier is cheaper.

Yep, I spent 4 weeks worth of full time hours reading catalogues, drawing things in CAD, running FEA and calling strangers for advice and help just because I dislike cross-drilled rotors...
 

Davidt99

Member
Messages
184
This has been an interesting read but I didnt see anywhere about type approval. Not sure where you are based but if in the UK do you know how to get type approval so that you can use the brakes on your car?

 

lambertius

Banned
Messages
341
This has been an interesting read but I didnt see anywhere about type approval. Not sure where you are based but if in the UK do you know how to get type approval so that you can use the brakes on your car?


Based in Australia. I know it isn't an issue for me locally, and the rotors themselves are complied in a bunch of regions around the world. I read the link, it sounds like type approval is a manufacturer level thing? What's the go with modifying vehicles in the UK?

Locally, a vehicle is only modified if you hit a bunch of specific checks. They're do with changing wheel sizes beyond a certain amount, suspension beyond, or changing the induction type of an engine, and probably a bunch of others I don't recall. I have ITBs on my BMW but it isn't a modified vehicle as I haven't changed the induction type, as an example.
 

lambertius

Banned
Messages
341
I did some shopping today!

DBA5048.1L/R $527.8
DBA52650.1 $441
Front and rear hats in 6061-T6 anodised red $378.4
24xMS20004-6 $124.08
16xMS20004-28 $93.28

So all in $1564.56AUD for everything front to rear - about 860GBP in today's trading.

I was recommended a different machinist who absolutely savaged any competitor quotes for the hats, so I'm going with them. I also got super lucky with the rotors, a retailer here was having a one day sale for first responders that was 30% off. My fiancee and I are both away for work, but my girlfriend is home and she is a nurse so I called her and she went by and grabbed the parts for me!

I still have to get the rear rotors machined, and hopefully I get it right the first run, but overall it has come in a fair bit cheaper than I had originally anticipated!